1、Surface plates Cast iron surface plates Requirements and testing Prfplatten; Prfplatten aus Gueisen; Anforderungen, Prfung This standard, together with the August 1984 edition of DIN 876 Part 1, supersedes the May 1972 edition of DIN 876 In keeping with current practice in standards published by the
2、 International Organization for Standardization (/SO), a comma has been used throughout as the decimal marker. Dimensions in mm 1 Scope and field of application This standard applies to cast iron surface plates which are used as a plane, or datum surface in dimensional metrology, in particular in te
3、sting for deviations of form or position. biN 876 Part 2 2 Dimensions, designation 630 800 1000 1250 1600 1800 .- Figure 1. Dimensions 800 25 1000 25 1250 30 1600 30 1800 40 2000 40 Table 1. Dimensions - Term I DIN number Length X width (I X b), in rnm Material : cast iron . _.- 2000 31 50 40 Detail
4、 50008000 50 131 505000 50 i 1 pg 1 ; I 1 600 48 2000 22 38 2500 27 46 4000 42 71 108 The number, type and width a (in accordance with DIN 6501, the position of guiding faces (in the case of guide slots) and, if required, a tolerance on parallelism to a side face and the accuracy grade shall all be
5、subject to particular agreement. 3.7 Tapped holes and fitting holes By particular agreement, both tapped holes (not exceeding size M 8) and fitting holes may be drilled in the working surface. 3.8 Side faces By agreement, cast iron surface plates may be fitted with extra-wide side faces. Specificati
6、ons as to the flatness and perpendicularity of such side faces shall also be agreed upon separately. They may be provided with tapped holes for attaching any test or safety equipment required. 3.9 Edges and border zone The toleranced surfaces may be surrounded by a border zone, the width of which sh
7、all not exceed 2 % of the width b, or 20 mm, whichever is smaller. The edges and corners of the toleranced surfaces shall be chamfered as shown in figure 1, detail Z. 3.10 Rigidity To prevent undue deflection occurring under load, the manufacturer shall furnish the surface plates with adequate ribbi
8、ng. Note. The rigidity of cast iron surface plates depends to a very great extent on the underside ribbing. 3.1 1 Material and finish Material: cast iron with lamellar graphite (GG) as Finish: toleranced surfaces shall be planed, shaped or specified in DIN 1691,gradesubject toagreement. milled, and,
9、 if required, scraped. 4 Testing Testing shall be performed without load being applied to the surface plate. The surface plate shall stand level on the supporting feet provided. The border zone described in subclause 3.9 shall not be included in the area tested. 4.1 Bearing area Bluing with a second
10、 surface plate shall be used to establish the bearing area of a surface plate. For surface plates with lengths 1 of 2500 mm or less, the bluing plate shall be 250 mm square, and for surface plates of greater length, 400 mm square. Both surface plate and bluing plate shall be thoroughly degreased bef
11、ore bluing is carried out. A 50 mm X 50 mm glass plate, or other suitable device, shall be used to count the number of high spots at random points on the working surface. 4.2 Waviness Measurement of the depth of waviness shall comply with the specifications of DIN 4774, except that the values given
12、there for the waviness measuring length l, and the cut-off wavelength At shall be amended to I, = 40 mm and At = 2,5 mm, respectively. 4.3 Flatness overall of working surface The flatness test shall be based on a grid of measuring points such as is shown in figure 4, the points being set at interval
13、s corresponding to the base length 1, of the test device used. Suitable instruments for performing this test are pendulum inclinometers, autocollimators or laser interferometers. Such instruments measure tilts directly, and these may be converted into deviations in height by reference to the base le
14、ngth Ig. The recommended base length is lB = 1 O0 mm; the guideline value for the diameter of the pads, which shall be coplanar, is 18 mm. For accuracy grades 1 to 3 surface plates, it is permitted to carry out the test using an accuracy grade O0 straightedge as specified in DIN 874 Part 1. l-4 Figu
15、re 4. Grid of measuring points (example) *) See page 2. COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling ServicesPage 4 DIN 876 Part 2 4.4 Local flatness of working surface For local areas of the working surface, testing is limited to checking the deviation
16、from straightness of profile lines at randomly selected points on the working surface; the length of the profile line under examination shall not be less than 2 1 and not exceed 354 mm (length of the diagonals of the local area of the working surface). The deviations from straightness thus determine
17、d shall not exceed the flatness tolerances specified in table 6. A straightedge conforming to DIN 874 Part 1 may be used as a straightness standard. 5 Marking Surface plates conforming to the present standard shall display the following marking on one of the side faces: a) DIN876; b) accuracy grade;
18、 c) manufacturers trade mark or name. 6 Advice to users The floor area on which the surface plate stands shall be solid, rigid, flat and level; special foundations may be required to support large surface plates which have a high unloaden mass and which are subjected to heavy loading. Cast iron surf
19、ace plates are suitable as bases for the tempering of test objects. Standards referred to DIN 650 Machine tools; T-slots, dimensions DIN 874 Part 1 Steel straightedges: dimensions, technical delivery conditions DIN 1691 DIN 4774 Cast iron with lamellar graphite (grey cast iron) Measurement of the de
20、pth of waviness by means of electrical contact stylus instruments Other relevant standards DIN 102 DIN 874 Part 2 DIN 876 Part 1 Reference temperature for measuring tools and workpieces Knife-edge straightedges; dimensions, technical delivery conditions Surface plates; natural hard rock surface plat
21、es, requirements and testing Previous editions DIN 876 Part 1: June 1950; DIN 876 Part 2: October 1931x; DIN 876: October 1931, May 1972. Amendments The following amendments have been made in comparison with the May 1972 edition of DIN 876: a) The contents have been divided into Part 1, dealing with
22、 natural hard rock surface plates, and Part 2, dealing with cast b) Translators note. Amendment b) refers to a change in nomenclature that does not affect the English translation and c) No fixed dimensions have been specified for the sizes of the surface plates, only ranges for the length 1. d) Requ
23、irements relating to a local area of the working surface have been specified. e) Requirements relating to guide slots (if provided) have been specified. f) Requirements relating to waviness have been specified. g) The specification of shapes of ribbing has been dropped from the standard. h) Tests ha
24、ve been specified. i) A clause on advice to users has been incorporated. j) The reference area for the number of high spots has been altered. k) Marking has been included in the standard specifications. iron surface plates. has thus been omitted. Explanatory notes ISOTTC 3/SC 3 is at present engaged
25、 in the preparation of two standards dealing with surface plates. This standard has incorporated some of the interim results of that work, but the competent subcommittee of the Normenausschuss Linge und Gestalt (Length and Shapes Standards Committee) has decided not to adopt the proposed internation
26、al standards in their entirety, not least because closer tolerances are considered desirable in Germany. Re clause 2 As the dimensional specifications included in previous editions have hardly ever been adopted in practice, the present standard only specifies size ranges for the length I; it is thus
27、 necessary when designating or ordering surface plates to specify the actual length and width. COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling ServicesDIN 876 Part 2 Page 5 Re subclause 3.2 Experience has shown that the previous requirement in respect of hi
28、gh spots was set too high. The reference area must be increased fourfold, .e. to 50 mm X 50 mm, for the required counts to be obtained. Re subclause 3.5 In order to ensure adequate accuracy in small areas even in the case of large surface plates, a flatness tolerance t2 has been specified for any 25
29、0 mm square local area of the working surface. Re subclause 3.10 As the various forms of ribbing specified in previous editions have never been applied in practice, no data have been included here in that respect. It ought to suffice for the manufacturer to furnish surface plates with the form of ri
30、bbing which he has found by experience to ensure an adequate degree of stability and rigidity. Re subclause 4.3 Grids of measuring points which are required for testing the flatness of working surfaces and which can be framed within the side lines and diagonals, are drawn up with the aid of combinat
31、ions of Pythagorean (triangular) numbers. Some examples of such ratios are given below: Table 9. I m:n:o rn 20 : 21 : 29 3: 4: 5 8:15:17 5: 12: 13 12 : 35 : 37 7 : 24 : 25 9 : 40 : 41 a 43,6030 36,870 28.072O 22,620 16,925 1 6,260 1 2,680 Re clause 5 As international standards also employ arabic num
32、erals to denote accuracy grades, it has been decided to include the DIN number, DIN 876, in the marking of surface plates which conform to the present standard so that doubts may not arise as to which standard a surface plate conforms, once the international standards pertaining to surface plates have been published. This suggestion in respect of marking has also been adopted for the proposed international standards on surface plates. International Patent Classification B 25 H 7-02 COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling Services
